Process for the production of aromatic hydrocarbons



etc.

Patented July 10, 1945 UNITED STATES PATENT OFFICE- PROCESS FOR THEPRODUCTION OF AROMATIC HYDROCARBONS Kenneth C. Edson and Frank E.Fisher, Pawhuska, kla., assignors to Skelly Oil Company, Tulsa, Okla, acorporation of Delaware No Drawing. Application May as, 1943, Serial No.488,888

14 Claims. (Cl. 260-45735) It is well known that aliphatic hydrocarbonsmay be converted to aromatic hydrocarbons by subjecting an aliphatichydrocarbon to elevated temperatures in the presence of a cyclizing anddehydrogenating catalyst. Catalysts of this type which have beenproposed in the past may comprise the oxides or other compounds ofvanadium, chromium, molybdenum, titanium, zirconium, cerium, hafnium,thorium, colum'bium, tantalum, tungsten, uranium, etc., deposited on asuit- 15 lyst to be used in the process of this invention,

able carrier or support such as activated alumina, bauxite, bentonite,kieselguhr, glauconite and the like. For example, suitable aromatizationcatalysts may contain a major proportion of aluminum oxide as a carrierand a minor proportion of chromium oxide, vanadium oxide or molybdenumoxide as the active ingredient. I

In accordance with the present invention, it has been discovered thatthe efliciency of aromatization catalysts can be improved to increasethe yield of aromatic compounds when used in an aromatization process bythe addition of rela-'- tively small amounts of barium peroxide thereto.The barium peroxide serves as a promotor or activator for the catalystand increases the efiiciency of the catalyst in a process for theconversion of straight-chain hydrocarbonsfto aromatic hydrocarbons.

In accordance with the present invention, aromatic hydrocarbons areproduced from aliphatic hydrocarbons by subjecting the aliphatichydrocarbonsat elevated temperatures to an aromatization catalyst havingbarium peroxide associated therewith. The, aromatization catalyst itselfmay comprise chromium oxide, vanadium oxide, molybdenum oxide, or thelike and the catalyst and barium peroxide may be supported on anysuitable carrier such as bauxite, activated alumina, bentonite,kieselguhr, crushed silica,

In accordance with prior art processes, an aromatization catalyst may beproduced by precipitating an oxide or other compound of chromium,vanadium, molybdenum, or the like with alumina to form a gel which isthereafter dried to form the desired catalyst. If desired, =alumina maybe impregnated directly with a solution of a. salt or acid of chromium,vanadium, molybdenum, or the like and subsequently dried to form thecatalyst. However, irrespective of the manner in which the catalyst maybe formed,

it has been found, in accordance with the present invention, that theaddition of barium peroxide to the catalyst increases its activity to a.substantial degree, thus making it capable of producing yields ofaromatic hydrocarbons higher than heretofore obtainable when aliphatichydrocarbons are passed at elevated temperatures thereover. The catalystand its preparation forms no part 10 of the invention claimed in thisapplication, but

has been more specifically pointed out and claimed in our co-pendingapplication Serial No. 468,110, fil ed December 7, 1942.

In the preparation of the highly active catathe barium peroxide may beadded to the catalyst as such or it may beformed directly within thecatalytic mass from-compounds of barium that are convertible to theperoxide. For exampie, barium oxide (BaO) may be added directly to thecatalyst and then converted to the peroxide (132102) by heating thecatalyst to a temperature between 500 and 600 C. in the presence of airor other oxygen-containing gas. Thus it is possible to use, instead ofbarium peroxide, barium oxide or one of the soluble salts of bariumwhich will decompose to the oxide on heating and which then in turn maybe oxidized to form the peroxide at an elevated temperature as indicatedabove. A unique property of the barium oxides is that the peroxidedecomposes again to the monoxide at a temperature of about 800 to 900 C.Accordingly the catalyst containg barium perodixe should not be allowedto reach this temperature 5 even when being regenerated, not onlybecause of the decomposition of the barium peroxide, but also becauseheat to temperatures above 900 C. has a tendency to destroy the activityof the chromium, molybdenum, or vanadium oxide cata- 40 lysts. However,even though such a temperature is reached, the barium oxide canbereoxidized to the peroxide in the presence of air or oxygen at the lowertemperature.

In the preparation of the catalyst to be used in accordance with thisinvention certain precautions should be observed, as pointed out in ourabove referred to co-pending patent application. Qrdinarily the use ofwater or aqueous solutions should be avoided in that step of the processin which the barium oxide or barium peroxide is to be admixed with thecatalyst.

Both barium oxide and barium peroxide reactwith water to form bariumhydroxide which is stable and will not decompose to the oxide except asat temperatures of approximately '1000 C.

accordance with the processof this invention,

the following proceduresmay be used. However, it is to be understoodthat this invention is not to be limited to the use of the specificcatalysts disclosed in the following examples:

PREPARATION I Ten to twelve mesh granules of activated aluminaareimpregnated with a solution of chromic acid (H2Cr04) or chromic nitrate(Cr(NO3)3) of such a concentration and in such an amount as to give ondecomposition 8 per cent of chromium sesquioxide (CI'2O3) on thealumina. The resulting product is evaporated to dryness on a hot plateat a temperature below 190 C. The catalyst is then wet with somenonionizlng solvent other than water and 8 per cent of powdered bariumoxide or barium peroxide is mechanically stirred intothe mixture. Ifbarium peroxide is used, the catalyst is ready for immediate use. In theevent that barium oxide is used, the catalyst is heated to between about500 and 600 C. in the presence of air or oxygen for a period of aboutone hour so as to oxidize the barium oxide t the peroxide.

PREPARATmia II Chromic acid is placed on activated alumina and dried asin Preparation I supra. The chromic acidfanhydride (CrOa) thus formed isthen reduced to the sesquioxide by heat, or by contact with a reducingsubstance- The resulting mass is then impregnated with a solution of a.salt of barium that will give the oxide on heating, for example, bariumnitrite (Ba(NOa)a). The

PREPARATION VI This process is the same as Preparation II, supra, exceptthat ammonium molybdate is substituted for the chromic acid.

The foregoing examples of the preparation of an improved catalystcomprising chromium, vanadium or molybdenum sesquioxides deposited on analumina support and activated by barium peroxide are presented hereinmerely as examples which are susceptible to various modifications. Thisinvention is not to be considered as limited to methods involving theexact chromium, vanadium, molybdenum, barium, or other compounds amountof the salt of barium that is used is such a as to give an 8 per centconcentration of barium peroxide when the mixture is eventually heatedin the presence of oxygen to form the barium peroxide.

PREPARATION III The same procedure 1s followed as indicated inPreparation I, supra, except that ammonium vanadate (NH-N03) issubstituted for the chromic acid or chromic nitrate. The" resultingcatalyst comprising a mixture of activated alumina, vanadium sesquioxide(V203) and barium peroxide is a very active aromatization catalyst.

PREPARATION IV This preparation is the same as Preparation II, supra,except that ammonium vanadate is substitutedfor the chromic acid.

PREPARATION V 51:, This method is the same as Preparation 1, supra,except that ammonium molybdate is substituted for the chromic acid orchromic nitrate. The resulting catalyst containing activated alumina,molybdenum sesquioxide (M0203) and barium peroxide is a highlyefiicacious aromatization catalyst.

mentioned above or to methods employing the "exact proportions ofingredients specified. For

example, the oxides or other compounds of titanium, zirconium, cerium,hafnium, thorium, columfound to be particularly useful, other supportsor carriers may be substituted therefor or admixed therewith, suchsupports or carriers being magsupported on any suitable "carrier.

' The" improved catalysts of the present invention may be employed asaromatization catalysts for the conversion of hydrocarbons having fromsix to twelve carbon atoms, or as combined crackingandaromatizationcatalysts for hydrocarbons ranging up to twenty carbonatoms. The use of these catalysts with hydrocarbons having from six totwelve carbon atoms has already been described and claimed in ourapplication Serial No. 468,111, filed December 7, 1942, and the presentapplication is to be considered as a continuationin-part of saidapplication Serial No. 468,111, we having found that, contrary to whatwould normally have been expected, hydrocarbons having more than twelvecarbon atoms were also capable of conversion into aromatic (i. e. cycliccompounds by the use of catalysts containing barium peroxide.

To illustrate the superior activity of the im- I proved catalyst havingbarium peroxide associated therewith, a comparison of the activity ofcatalysts with which barium peroxide has and has not been associated hasbeen made. In one series of these comparative tests normal heptane waspassed over the several catalysts at about 550 C. at atmosphericpressure and with a contact time of about 15 seconds. The followingTable A shows that the conversion of heptane to toluene wassubstantially greater when passed over those catalysts containing bariumperoxide:

assopss' 3 It willbe seen from the above data of Table A that theactivity of a catalyst containing 8 per cent of barium peroxide wasapproximately 20 per cent greater than that of a catalyst which did nothave any barium peroxide associated therewith, when employed for thearomatization of heptane. In connection with the experiments which wererun to obtain the above indicated data it was observed that the rate ofcarbon formation due to side reactions was much less when the catalystcontaining barium peroxide was used,

thus permitting longer operating periods between regeneration.

To further illustrate the superior activity of the improved catalysthaving barium peroxide assoelated-therewith, a comparison of theactivity of catalysts with which barium peroxide has and has not beenassociated has also. been made with hydrocarbons having a larger numberof carbon atoms. In these further comparative tests, heavy straightrungasoline. (B. P. 128 to 209 C.) kerosene (B. P. 169 to 263 C.), andgasoil having an end point of 371 C. were passed over the differentcatalysts at about 490 C. at atmospheric pressure and with a contacttime of about 15 seconds. The following Table 13 shows thattheconversions of such hydrocarbons were greater when passed over thosecatalysts containing barium peroxide:

, Table B Once-through Catalyst ggg 'ig CHARGE: HEAVY STRAIGHT RUNGASOLINE CHARGE: 311 0. END POINT oss OIL I gZZAhOH-S CnOs 48 A110. cnosi syfisaIIIIIIIIIIIIIIIIIIII 51 It will be seen from the above data thatthe activity of a catalyst containing 8 per cent of barium peroxide wasapproximately 10 per cent greater than that of a catalyst which did nothave any barium peroxide associated therewith. In connection with theexperiments listed in Table B, it was also observed that the rate ofcarbon formation due to side reactions was much less when the catalystcontaining barium peroxide was used, thus permitting longer operatingperiods between regenerations.

The products obtained when operating under V the conditions indicated inTable-B, and which were made with the catalysts containing bariumperoxide, had relatively high octane number, and were found to besuitable for use as a motor fuel and, due to the combination crackingand aromatization reaction, boiled largely within the gasoline boilingpoint range.

The foregoing data is intended merely to illustrate theefliciency oi theherein described barium peroxide-containing catalyst and is in no wise-to be considered as a limitation on the type of process in which thisinvention can be used. It has been-found that aromatization ofhydrocarbons by the herein described catalyst may be ,pheric pressuresare ordinarily preferred but subatmospheric or superatmosphericpressures may be employed if desired. The process is applicable to thetreatment of hydrocarbons having from about six tov twenty carbon atoms.Where both cracking as well as aromatization is involved, theboilingpoint range is about from 215 C. to 370 0., Also to increase thepercentage of over-all conversion of aliphatic hydrocarbons to aromatichydrocarbons, recycling may be employed.

The relative proportions ofinsredients in the active catalyst used inthe process of this invention may vary within wide limits. However, thesupport or carrier preferably constitutes a major proportion by weightof the catalytic body and suitably 50 to 92 per cent; and the otheringredient preferably constitutes a minor proportion by weight of thecatalytic body, the barium peroxide being suitably present in amountsbetween about 4 and 25 per cent, and the chromium, vanadium ormolybdenum sesquioxide or other catalytic substance being suitablypresent in amounts between about 4 and 25 per cent.

While several particular embodiments of this invention are shown above,it will be understood, of course, that the invention is not to belimited thereto, since many modifications may be made, and it iscontemplated, therefore, by the appended claims, to cover any suchmodifications as fall within the true spirit and scope of thisinvention.

We claim:

1. A process for the production of aromatic hydrocarbons from aliphatichydrocarbons which comprises subjecting the aliphatic hydrocarbons atelevated temperatures to a catalyst comprising an oxide selected fromthe group consisting of vanadium oxide, molybdenum oxide and chromiumoxide, in admixture with barium peroxide.

2. A process for the production of aromatic hydrocarbons from aliphatichydrocarbons having from about 6 to about 20 carbon atoms whichcomprises subjecting said aliphatic hydrocarbons to atemperaturesuflicient to eflfect cracking, dehydrogenation and cyclization in thepresence oi. a catalyst comprising barium peroxide and a compoundselected from the group consisting of chromium oxide, molybdenum oxideand vanadium oxide. I

3. A process for the production of aromatic hydrocarbons from aliphatichydrocarbons having from about 6 to about 20 carbon atoms whichcomprises subjecting said aliphatic hydrocarbons to a temperaturebetween-about 450 and 750 C.

in the presence of a catalyst comprising barium peroxide and a compoundselected from the group consisting of chromium oxide, molybdenum oxideand vanadium oxide. a

4. A process or the production of aromatic hydrocarbons from aliphatichydrocarbons havins from about 6 to about 20 carbon atoms whichcomprises subjecting said aliphatic hydrocarbons to a temperaturebetween about 450 and 750 C. in the presence of a catalyst comprisingbarium peroxide and a compound selected from the group consisting orchromium oxide, molybdenum oxide and vanadium oxide tor a period or timefrom about 1 to less than about 25 seconds. 5. A process for theproduction of aromatic hydrocarbons from aliphatic hydrocarbons whichcomprises subjecting said aliphatic hydrocarbons at elevatedtemperatures to a catalyst comprising a major proportion of an aluminumoxide support and minor proportions of barium peroxide and a compoundselected from the group consisting of chromium oxide, molybdenum oxideand vanadium oxide.-

6. A-process for the production of aromatic hydrocarbons from aliphatichydrocarbons having from about 6 to about 20 carbon atoms whichcomprises subjecting said aliphatic hydrocarbons to a temperaturesufilcient to efiect cracking, de-

hydrogenation and cyclization in the presence of a catalyst comprisingmore than about 50 per cent of activated aluminum oxide, less than about25 per cent of barium peroxide and less than about 25 per cent of acompound selected from the group consisting of chromium sesquioxide,

molybdenum sesquioxide and vanadium sesquioxide.

'1. A process forthe production of aromatic hydrocarbons from aliphatichydrocarbons having from about 6 to about 20 carbon atoms whichcomprises subjecting said aliphatic hydrocarbons to a temperaturebetween about 450 C. and about 600 C. for a period of time between aboutll and 25 seconds in-the presence of a catalyst comprising a majorproportion of an activated aluminum oxide support admixed with minorproportions of barium peroxide and a compound selected from the groupconsisting of chro- I mium sesquioxide, molybdenum sesquioxide andvanadium sesquioxide.

8. The process recited in claim 7 wherein said aliphatic hydrocarbonscomprise heptane and the hydrocarbons from aliphatic hydrocarbons whichcomprises subjecting the aliphatic hydrocarbons to a temperaturesufliclent to efiect aromatization in the presence of barium peroxideand molybdenum oxide.

11. A process for the production of aromatic hydrocarbons from aliphatichydrocarbons which comprises subjecting the aliphatic hydrocarbons to atemperature suiijicient to effect aromatization in the presence ofbarium peroxide and vanadium oxide.

12. A process for the production of aromati hydrocarbons from aliphatichydrocarbons having from about 6 to about 20 carbon atoms whichcomprises subjecting said aliphatic hydrocarbons to a temperaturebetween about 400 C. and about 700 C. for a period of time between about1 and 25 seconds in the presenceof a catalyst comprising a majorproportion of an activated aluminum oxide support admixed with minorproportions of barium peroxide and chromium sesquioxide.

13. A process for the production of aromatic hydrocarbons from aliphatichydrocarbons having from about 6 to about 20 carbon atoms whichcomprises subjecting the aliphatic hydrocarbons to a temperature betweenabout 400 C. and about 700 C. for a period of time between about 1 and25 seconds in the presence of a catalyst comprising a major proportionof an activated aluminum oxide support admixed with minor proportions ofbarium peroxide and molybdenum sesquioxide.

14. A process for the production of aromatic hydrocarbons from analiphatic, hydrocarbon having from about 6 to about'20 carbon atomswhich comprises subjecting sa/ld aliphatic hydrocarbons to a temperaturebetween about 400 C., and about 700 C. for a period of time betweenabout 1 and 25 seconds in the presence of a catalyst comprising a majorproportion of an activated aluminum oxide support admixed with minorproportions of barium peroxide and vanadium sesquioxide. i

KENNETH C. EDSON. FRANK E. FISHER.

